Elasticarubber fig treegrowing tipmeans what you think it does – stretchable, rubbery, referring to the latex sap. The word is botanical Latin rather than classical Latin.

This is not an Australian native, but comes from an area stretching from north-eastern India (Assam) to the islands of Sumatra and Java. One tree photographed is in Barbarra Street, ‘over the creek’ in Picnic Bay, and rather sprawls among other trees by the roadside. There are several of the plants in a hedge-line between two properties. The large buttressed tree is in Nelly Bay.

The rubber fig is a fat bush in the banyan group of figs, and in the right conditions can grow to 30 or 40 m in height, with a stout trunk up to about 2 m in diameter. It will develop aerial and buttressing roots to anchor it to the soil and help support the heavy branches. It has broad shiny oval leaves up to 35 cm long and 15 cm broad, with the leaf sizes greater on young trees, and gradually lessening as the tree matures. The leaves develop inside a pinkish sheath at the apical meristem, which grows larger as the new leaf develops. When it is mature, it unfurls, and the sheath drops off the plant. Inside the new leaf, another immature leaf is waiting to develop.

leaves & figsAs with other members of the genus Ficus, the flowers require a particular species of fig wasp to pollinate them, and are contained within the fruit, a small yellow-green fig about 1 cm in diameter, barely edible. It will not produce viable seed unless the relevant wasp is present. The wasp for this species is Pleistodontes clavigera.

In temperate climates, this is a popular house plant. It does not need as much light as many other indoor plants, it is willing to endure a considerable amount of neglect, and its stems are sufficiently strong so as not to require staking. It does, however, do better with as much light as possible, except that full midday sun through glass will probably be too much for it. It is highly susceptible to root rot through over-watering (the plant will die!), and quite unforgiving to critical under-watering (it will drop its leaves). It is actually possible to train the plant to hydroculture – it needs a great deal of care during its conversion: it must be kept warm, be provided with extra humidity if the air is too dry, and not be moved to an area with lower light levels or cooler temperature at any time during the conversion. It will quite quickly develop its water roots and flourish in its new growing style. Indoors, the plant can reach about 2.5 m in height. The tree is propagated by seeds (when available), by cuttings, or by layering.

A fascinating use of the tree is that the Khasi people of north-eastern India build bridges with it. They do this, not by felling the tree and using the logs, but by using the aerial roots, while the tree is alive and growing. A Ficus elastica tree is located near the spot where a bridge is needed. If there is another on the opposite side of the stream, it is utilized as well. A betel-nut tree is cut down, and its trunk hollowed out. The hollowed trunk is placed across the stream, and an aerial root from the Ficus is guided into the hollow trunk. The root grows along the trunk until it reaches the soil on the other side, when it roots into the soil. Over time, the betel-nut trunk rots away, the Ficusroot grows and thickens, and eventually you have a solid bridge strong enough to walk over. The process takes some 10 – 15 years here, in an area of dense natural forests and an almost unbelievable amount of monsoonal rain. Sometimes people stretch aerial roots from the trees to points along the edges of the bridge, forming what are more-or-less suspension cables and railings. There is even a double-decker bridge in one place.